What we do

The purpose of the improvement project relating to the access channels of the Port of Rouen is to deepen the River Seine to increase the admissible draught of ships by one metre. The Seine’s navigational channel had to be deepened in various sections between Rouen and Courval, representing a stretch of more than 46 km. The navigational width of the channel will then be increased from -6.50 m CMH to -8.50 m CMH.

Dredged materials were hydraulically pumped and brought to dry land and discharged in three locations in Moulineaux and Saint-Wandrille for recycling and in the Marais ballast pit at Yville-sur-Seine for filling. In certain emergency situations, some of the materials could be piled in certain specific immersion zones in the Seine.

The nature of the dredged materials is highly variable, ranging from clay to gravel, more or less loosely packed. Some of the zones in particular underwent a specific DSD pre-treatment to disintegrate the materials before their removal by a suction dredge.

This complex project was successfully completed despite several challenges which included:

• Strong tidal currents due to rapidly changing tides.
• Transport of the heavy materials ashore over a distance of up to 1.5 km with relay stations.
• Management of pumped water in the three sites, requiring the installation of heavy-duty pumps.
• Elevated level of wear owing to the abrasiveness of the materials and requiring special equipment inspections and preventive maintenance operations.
• Very stringent dredging tolerance mechanisms for acceptance in the dedicated zones.
• Environmental monitoring of the waters discharged in the Seine and coming from the dry land sites (flow rates and suspended solids).
• Particular constraints related to noise nuisance, with restrictions on the work hours for backfill operations.
• Specific conditions of working in a river with heavy traffic.